Porous styrene polyfunctional methacrylate polymers

ABSTRACT

A porous copolymer resin containing a major amount of styrene, or other aromatic vinyl constituent, and cross-linked with a minor amount of an aliphatic polyfunctional methacrylate having at least three methacrylate groups such as trimethylolpropane trimethacrylate. The resin is prepared by suspension polymerization and is thereafter given a chloromethylation and aminolysis treatment to convert it into a strong base resin. Other methods of preparing the strong base resins not involving direct chloromethylation can also be used. The resin shows unusual physical stability and is particularly useful in stringent applications such as the recovery of uranium complexes from acidic leach liquors.

United States Patent [1 1 Clemens et al.

[ POROUS STYRENE POLYFUNCTIONAL METHACRYLATE POLYMERS [75] Inventors:David H. Clemens, Willow Grove;

Herman C. Hamann, Melrose Park, both of Pa.

[73] Assignee: Rohm and Haas Company,

Philadelphia, Pa.

[22] Filed: Feb. 27, I974 [211 Appl. No.: 446,555

Related US. Application Data [63] Continuation-impart of Scr. No,267,336, June 29, 1972, Pat. No. 3,817,878, which is acontinuationJn-part of Ser. No. 155,279, June 21, 1971. abandoned, whichis a continuation-in-part of FOREIGN PATENTS OR APPLICATIONS 848,5559/1960 Great Britain [111 3,870,663 [451 Mar. 11, 1975 1,135,130 ll/l968Great Britain 1,566,019 5/1969 France 55,644 9/1968 Poland OTHERPUBLICATIONS Rohm & Haas, Brochure CM-32, June, 1969. Visnyakov,Vysokomol. Soedin. 7, 239-44( 1965).

Davankov et al., Vysokomol. Soedin. 4, 1093-97( 1962). Davankov et al.,Zhur. Priklad. Khim. 34,

Primary ExaminerMe|vin Goldstein Attorney, Agent, or FirmH. JolyonLammers [57] ABSTRACT A porous copolymer resin containing a major amountof styrene, or other aromatic vinyl constituent. and cross-linked with aminor amount of an aliphatic polyfunctional methacrylate having at leastthree methacrylate groups such as trimethylolpropane trimethacrylate.The resin is prepared by suspension polymerization and is thereaftergiven a chloromethylation and aminolysis treatment to convert it into astrong base resin. Other methods of preparing the strong base resins notinvolving direct chloromethylation can also be used. The resin showsunusual physical stability and is particularly useful in stringentapplications such as the recovery of uranium complexes from acidic leach1iquors.

7 Claims, N0 Drawings POROUS STYRENE POLYFUNCTIONAL METHACRYLATEPOLYMERS This application is a continuation-in-part of our earlier filedand copending application, Ser. No. 267,336 now US. Pat. No. 3,817,878filed June 29, 1972, entitled Strong Base Anion Exchange Resins which inturn is a continuation-in-part of our earlier filed and copendingapplication, Ser. No. 155,279 filed June 21, 1971, and now abandonedentitled Strong Base Anion Exchange Resins which in turn is acontinuation-inpart of application Ser. No. 884,325, filed Dec. 11,1969, now abandoned.

This invention relates to strong base anion exchange resins and to theirpreparation and use. The resins have a backbone of styrene or othersuitable aromatic monovinyl hydrocarbon in major amount, crosslinkedwith a minor amount of an aliphatic polyfunctional (at leasttrifunctional) trimethacrylate, such as trimethylolpropanetrimethacrylate, pentaerythritol trimethacrylate or tetramethacrylate,or the like. The resins are prepared by the suspension polymerization ofthe styrene or other aromatic vinyl constituent and the crosslinkingmonomer, and are thereafter chloromethylated and aminolyzed to introducethe desired functional groups.

The prior art has suggested the use of difunctional aclinkers under someconditions do or may show a lack of physical or chemical stability orperformance characteristics. The prior art has even suggested thattrimethylolpropane trimethacrylate might be useful in ion exchangeresins. However, when trimethylolpropane trimethacrylate was used as acrosslinker in the attempted preparation of styrene based strong acidcation exchange resins, the styrene/trimethylolpropane crosslinked beadsupon sulfonation with concentrated sulfuric acid decrosslinked anddissolved. It is surprising, therefore, that polyfunctionalmethacrylates, such as trimethylolpropane trimethacrylate, have suchoutstanding utility in the preparation of styrenebased strong base anionexchange resins, as will be demonstrated more fully hereinafter.

More particularly, the resins of this invention are the reactionproducts of a tertiary amine and an insoluble, crosslinked copolymer ofan aromatic monovinyl hydrocarbon and an aliphatic polyfunctionalmethacrylate crosslinking agent containing at least 3 methacrylategroups, which copolymer contains haloalkyl groups having the formula-C,,H ,,X in which X is a chlorine or bromine atom and -C,,H is analkyene group in which n is an integer from one to four. The resins are,therefore, insoluble, predominately aromatic, crosslinked vinylcopolymers containing substituent groups having the general formula inwhich n is an integer of value one to four; R R and R are hydrocarbongroups at least one of which can be a hydroxy substituted hydrocarbongroup; and Y is an anion, such as a chloride, sulfate or hydroxyl ion.

In the preferred process, resins of the above type are readily preparedby a series of well-defined steps. An insoluble hydrocarbon copolymer isfirst prepared by copolymerizing a monovinly hydrocarbon such as styreneor vinly naphthalene and trifunctional methacrylate such astrimethylolpropane trimethacrylate. Haloalkyl groups are next introducedinto the insoluble copolymer by reacting the insoluble copolymer, in theform a small particles, with haloalkylating agents such as a mixture ofan aldehyde and a halogen acid (e.g., paraformaldehyde and hydrochloricacid) or a dihaloalkane and a Friedel-Crafts catalyst (e.g., ethylenedichloride and aluminum chloride) or a haloether and aluminum chloride)or a haloether and aluminum chloride as exemplified below. The resultanthaloalkylated copolymer is then reacted with a tertiary amine wherebythere is obtained an insoluble, crosslinked, polymeric, quaternaryammonium salt. A final washing with an hydroxide of an alkali metalconverts the quaternary ammonium salt to a quaternary ammoniumhydroxide. a

The final product, an insoluble, polymeric, quaternary ammoniumhydroxide, is extremely-basic; i.e., of the order of sodium hydroxide.When used in the treatment of acidic liquids and gases, the resinexchanges its hydroxyl groups for the anions present in the fluid withthe result that the acidity of the fluid is removed and the quaternaryammonium hydroxide is converted to a salt.

In the first step which involves the preparation of the hydrocarboncopolymer, a monovinyl hydrocarbon is polymerized together with atrifunctional methacrylate. That is, an aromatic hydrocarbon containingone vinyl substituent is copolymerized with a trifunctional methacrylatecontaining at least three vinyl substituents. Hy drocarbons of the firstclass are typified by the following: Styrene, ortho-, meta-, andparamethyl styrenes, ortho-, meta-, and para-ethyl styrenes, vinylnaphthalene, vinyl anthracene, and the homologues of the above. Whiletrimethylolpropane trimethylacrylate is the cross-linker of choice,other cross-linkers having at least three methacrylate groups which maybe used include, for example, pentaerythritol trimethacrylate ortetramethacrylate and glycerol trimethacrylate.

In preparing the copolymers a predominant amount on a weight basis ofthe monovinyl hydrocarbon is employed. That is, more than half of thetotal number of units, by weight, of hydrocarbon employed are those ofthe monovinyl hydrocarbon. It is preferred that the monovinylhydrocarbon constitute from to 99.9 percent, on weight basis of themixture of monovinyl hydrocarbon and cross-linking agent. That is tosay, it is preferred that the amount of the aliphatic cross-linkerconstitute 0.1 percent to 40 percent of the mixture on a weight basis,more preferably to 25 percent by weight, the balance in each instancebeing essentially the monovinyl aromatic hydrocarbon. The latter is across-linking agent which imparts insolubility, complexity, and hardnessto the copolymer. It has been shown that the use of even less than 0.1percent of the cross-linking agent will result in a copolymer which isinsoluble in organic liquids, although it may swell in some organicliquids. As the amount of cross-linker is increased, the resultantproduct becomes increasingly dense and corresponding difficult tohaloalkylate. Copolymers of a cross-linker and a mixture of two or moremonovinyl hydrocarbons are included within the scope of this invention.

The insoluble copolymers of this invention may be prepared by a varietyof well-known methods. Thus, the monomers may be mixed and thenpolymerized en masse or they may be emulsified or otherwise suspended ina liquid medium and then polymerized. Emulsionandsuspension-polymerization, in which the monomers are first suspended ina non-solvent for the monomers such as water or brine solution and arethen heated, agitated, and copolymerized, are much preferred becausethese methods yield hard copolymers in the form of small spheroids,globules, or beads and the size of such particles can be regulated andcontrolled. Thus, particles ranging in size from 5 to 325 mesh may beprepared. The extremely fine particles of approximately 40 to 150microns in diameter are particularly useful in certain new ion-adsorbingtechniques. Furthermore, very fine or porous particles may behaloalkylated and ultimately aminolyzed more rapidly and moreextensively than particles which are larger and/or more dense. Amodification of the suspension-polymerization method which produces verydesirable results involves suspending and polymerizing a solution of themonomers in a chemically inert solvent which is immiscible with thesuspending liquid and later removing the occluded or trapped solvent byleaching, drying, or distilling from the hard polymerized particles.This process yields particles of resin which are porous and which, dueto their porosity, react more readily. The resins of this invention canbe made up in gel form, as heretofore described, or they may be producedin macroreticular form by following the teachings of Meitzner et al;see, for example, British Pat. Nos. 932,125 and 932,126, or by othertechniques now known in the art.

The polymerization of the vinyl compounds is accelerated by means ofwell-known catalysts which provide oxygen. These catalysts includeozone, organic peroxidic agents typified by ozonides, peroxides such asacetyl peroxide, lauroyl peroxide, stearoyl peroxide, tert.- butylhydroperoxide, benzoyl peroxide, tert.-butyl perbenzoate, di-tert.-butyldiperphthalate, di-tert-butyl peroxide, and the barium salt oftert.-butyl hydroperoxide, inorganic agents such as barium peroxide,sodium peroxide, hydrogen peroxide and the so-called per" salts such asthe water-soluble perborates, persulfates, and perchlorates. Thecatalysts are employed in suitable amounts ranging from 0.l percent toabout 2.0 percent based on the weight of the monomeric material to bepolymerized.

The second step in the preparation of the products of this invention isone in which the insoluble, influsible, cross-linked polyvinylhydrocarbon is haloalkylated. This step involves introducing into thepolymer a plurality of bromoalkyl, or, preferably, chloroalkyl groups;that is, groups having the general formula C,,H ,,X as described above.While groups containing one to four carbon atoms are embraced by thisinvention, it is preferred to employ those compounds in whichchloromethyl groups, CH Cl, are added to the insoluble polymer, becausethe chloromethyl products are by far the most reactive. The carbon atomsin the group C,,H may be in a straight or a branched chain.

The step of haloalkylating the insoluble hydrocarbon copolymer may becarried out in a variety of ways. For example, the polymer may bereacted with a mixture of an aldehyde and hydrochloric acid or a mixtureof a dihalide and a Friedel-Crafts catalyst. Methods ofchloroalklylating which may be used for introducing the -CH Cl group andwhich also serve as guides for introducing C H X, C ,H X, and -C.,H Xgroups are described in Organic Reactions vol. I chapter 3, page 63 etseq. (John Wiley & Sons, Inc., N.Y.C., I942).

The extent of the haloalkylation reaction may be conveniently determinedby a halogen analysis. It is desirable that as many haloalkyl groups aspossible be introduced into the insoluble copolymer because the numberof such groups determines the number of qua ternary ammonium groups inthe final product; and, of necessity, the number of such quaternaryammonium groups determines the ultimate capacity of the resin to adsorbanions. Although resins containing relatively few quaternary ammoniumgroups have some capacity for adsorbing or exchanging anions, it isnecessary from a practical standpoint to add a large number of suchgroups in order to produce a resin of sufficiently high capacity as tobe commercially attractive. The minimum number of such groups should beone for every 15 aromatic hydrocarbon nuclei in the polymer. This, ofcourse, requires that at least one haloalkyl group be first added forevery 15 aromatic hydrocarbon nuclei; and in the case of achloromethylated copolymer of styrene and 1 percent trimethylol propanetrimethacrylate such a product would analyze about 2 percent chlorine.The upper limit is that reached when every available position in thearomatic nuclei is haloalkylated. Satisfactory resins of high capacitycan be made in which the number of haloalkyl groups, and, hence, thenumber of quaternary ammonium groups which are introduced is less thanthe theoretical maximum. Thus, very valuable resins are those made byaminating, with a tertiary amine, copolymers containing from 3 to 6haloalkyl groups for every four aromatic hydrocarbon nuclei.

The next step in the formation of the anion-exchange resin is theaminolysis of the haloalkylated copolymer with a suitable tertiaryamine. This reaction is preferably carried out by adding the amine tothe haloalkylated polymer while the latter is suspended and agitated ina liquid which is a solvent for the amine. The mixture may be allowed toreact at room temperature or, preferably, at elevated temperatures,after which the resin, containing quaternary ammonium salt groups, isfreed of the liquid.

The tertiary amine is usually used in the form of the free base.Tertiary amines containing unsubstituted hydrocarbon substituents aswell as hydroxy substituted hydrocarbon substituents are operable. Thehydrocarbon substituents of the amine may be alkyl groups, aryl group,cycloalkyl groups and aralkyl groups. Suitable tertiary amines aretypified by the following: Trimethyl amine, triethyl and tripropylamines, dimethyl ethyl amine, diethyl cyclohexyl amine, tricyclohexylamine, triphenyl amine, diphenyl ethyl amine, benzyl dimethyl amine,benzyl phenyl methylamine, dimethylaminoethanol, and the like.

As has been stated, the products of this invention are insoluble,infusible quaternary ammonium compounds. As prepared, they arequaternary ammonium salts; but

the salts may be readily converted into quaternary ammonium hydroxidesby washing with an hydroxide of an alkali metal.

The resins of this invention are quaternary ammonium compounds, and theresins in the form of the hydroxide are extremely strong bases whichneutralize acids and split salts. Their strength is like that of analkali-metal hydroxide, for example, sodium hydroxide. Thus, an hydroxylion of the resin may be exchanged for a chloride ion, a chloride ion fora sulfate ion, and so on; and the cation of the salt is not adsorbed.

Not only do these resins reduce acidity but they are capable of removinganions per se from salt solutions as well. Thus, when a solution ofsodium chloride is flowed down through a column of a resin of thisinvention in the hydroxyl form, the chloride ions of the salt solutionare exchanged for the hydroxyl groups formerly associated with theresin, and the liquid leaves the column as a solution of sodiumhydroxide. The resins may be regenerated by washing with a solution of astrong base such as sodium hydroxide. In addition to being chemicallyactive, the resins have such physical characteristics as to be capableof repeated use and regeneration in conventional water-treatingequipment.

The following examples serve to illustrate the preferred method ofpreparing the products of this invention. All parts and percentages areby weight unless otherwise stated.

EXAMPLE 1 a. An aqueous phase is made up with 1,018 parts of water, 2parts of polyacrylic acid dispersant, 0.9 parts of gelatin and the pHadjusted to about to 10 /2. The aqueous phase is charged to a 3 liter,3-neck flask fitted with stirrer, reflux condenser and nitrogen sweep.An organic phase consisting of 664 parts of styrene, 12.2 parts oftrimethylolpropane trimethacrylate and 6.8 parts of benzoyl peroxide isadded to the flask, stirring commenced at about 140-150 RPM withformation of a suitable dispersion. The reactor (flask) is heated toabout 80-82C. and held for about 3 hours at that temperature.Polymerization is completed by heating to 95 C. for a short time and theresultant slurry is filtered, washed and dried. Copolymer fractions inthe 20 +70 US. Standard Screen size are separated. The copolymeranalyzes about 98.2 percent styrene and 1.8 percent trimethylolpropanetrimethacrylate.

b. Chloromethylation and amination are carried out in a conventionalmanner; thus, the product ofa) above is slurried in a mixture ofethylene dichloride and chloromethyl methyl ether in a suitable flaskand heated to about 303 2C. and a catalyst such as Al C1 in additionalchloromethyl methyl ether (Ch -O-CH Cl) is added with stirring. Afterreaction is complete at 35 to 40C., the reaction mixture is cooled toabout 5C. and the excess aluminum chloride and chloromethyl ether isdecomposed. The copolymer beads are next aminolyzed with anhydroustrimethylamine at a temperature ranging initially from 5C. for about 1to 1.5 hours and then raising the temperature to 3035C. and holdingthere fore about 3 hours. After removal of excess amine, the slurry iscooled, washed with water, drained on a Buchner funnel, and packaged ina moist condition. The strong base anion exchange resin in the form ofaparticle size cut" comprising 90 percent retained on a 20 mesh screen,in a free hydroxide form (or chloride form) has a density of about 38pounds per cubic foot, a solids content of 44.8 percent. an anionexchange capacity of 50.2g/l of U 0 per liter of resin.

EXAMPLE 2 The procedure of Example 1 is repeated except that the levelof trimethylolpropane trimethacrylate crosslinker is adjusted in onecase to (a) 5 percent by weight and in another case (b) to 25 percent byweight. Stable copolymer beads are formed which can be subsequentlychloromethylated and aminated to form strong base anion exchange resins.

EXAMPLE 3 The strong base anion exchange resin of Example l(b) issubjected to a thermal shock test which illustrates the outstandingphysical stability of the resin. The resin is placed in cold water atl0-l2C. The water is drained and the resin contacted with 10 percent byvolume sulfuric acid at 60c. and maintained at this temperature forhour, Thereafter the acid solution is drained off and the resin placedin cold water at 10-l 2C. and maintained cold for /2 hour. percentperfect beads (i.e., none cracked or broken) are subjected to twentycycles of the test above. After twenty cycles 98 percent are stilluncracked and unbroken, i.e., still perfectly good. On the other hand, asimilar resin which is cross-linked with divinylbenzene shows after 20cycles in the same test only 47 percent uncracked beads.

The strong base anion exchange resin of Example 1 is subjected toanother test of physical durability, i.e., the pump test.

The pump test is a most severe test of physical durability. A cycleconsists of loading the resin for 4 minutes with 1N HCl, rinsing with HO for 3 minutes, draining for 30 seconds, regeneration for 4 minuteswith 1N NaOH, rinsing with H O for 3 minutes, and draining for 30seconds. The bed depth is ca. 2.2 and the pressure drop across the bedis maintained at 33 lbs./in. /ft. The main measure of durability is howdoes the flow rate change with cycling.

It can be seen in the table below (Table I) that the ion-exchange resinof Example l(b), compared with a similar resin but which is crosslinkedwith divinylben- The strong base anion exchange resin as prepared inExample l(b), i.e., in the chloride ionic form, gives particularly goodresults in the uranium recovery field. For example, the resin of Examplel(b) has a capacity of 50.2 g/l of U 0 per liter of resin. The uraniumforms anionic complexes with sulfate ions. e.g., UO (SO where n=l 2 or3, the most probable species cies present in solution being UO (SO Theresin can be used, for example, to absorb uranium (present as uranylsulphate) from an acid (usually sulphuric) solution thereof bycontacting the solution with the ion exchange resin at a pH of aboutl-5, most preferably about 3.3, containing about 0.01 g/l U and about 90g/l soluble sulphates. The loaded resin is eluted with 1.5 N H SO orwith chloride or nitrate ions in high concentration. In the finaloperation, the uranium is precipitated from the eluate with ammonia orsome other alkaline agent and the precipitate is filtered and dried.

The following example illustrates the preparation of a porous,macroreticular resin using an aliphatic polyfunctional methacrylatehaving at least three methacrylate groups as a crosslinker.

EXAMPLE 4 An aqueous phase is prepared having 1,590 parts tap water,10.7 parts of polyacrylic acid dispersant, 7.3 parts of gelatin, and thepH is adjusted to 10 to 10.5 with 50 percent NaOl-l. The above aqueousphase is charged to a liter, 3-neck flask equipped with a stirrer,reflux condenser and nitrogen sweep. An organic phase mixture containing880 parts of styrene, 120 parts of trimethylolpropane trimethacrylate,666.7 parts of methylisobutyl carbinol and parts of benzoyl peroxide isadded to the aqueous phase. Agitation is started at ll0l20 RPM usingintermittent stirring until a suitable dispersion is obtained. The flaskis heated to 70 C. in 1.5 hours then 70 C. is maintained for 10 hours.The methylisobutyl carbinol is removed by steam distillation inapproximately 6 hours. The copolymer is then washed and dried. Thecopolymer is then washed and dried. The copolymer is sieved and the +70mesh (U.S. Standard Screen size) is collected. The copolymer product isa porous macroreticular, resin and is composed of about 88 percentstyrene and l2 percent trimethyolpropane trimethacrylate and has aporosity of 0.42-0.43 cc/cc.

EXAMPLE 5 Chloromethylation are amination are effected in a conventionalmanner. The product of Example 4 above is slurried in a mixture ofchloromethyl methyl ether and ethylene dichloride in a suitable flaskand heated to 3032 C. for 1 hour. A catalyst such as AlCl (0.8 mole/morecopolymer) is dissolved in additional chloromethyl methyl ether; thenthe solution is added to the flask dropwise at 38-40 C. with stirring.The reaction is completed at 50 C. then the slurry is cooled to 5 C. andthe excess aluminum chloride and chloromethyl methyl ether isdecomposed. The beads are now aminolyzed with an aqueous solution oftrimethylamine. The amine is added dropwise at l0l5 C. over a l to 1.5hour period then the reaction is allowed to proceed at l0l 5 C. for 4hours. The excess amine is removed by steam distillation then the slurryis cooled, washed and packaged moist. The porous, macroreticular resinin a free hydroxide or chloride form has a solids content of 43.3percent and an anion exchange capacity of 4.14 meq./g.

EXAMPLE 6 The procedure of Example 5 is repeated but 1.0 moles AlCl/mole copolymer is used in the chloromethylation step. This resin in afree hydroxide form or chloride form has a solid content of 47.0 percentand an anion exchange capacity of 4.06 meq./g

The strong base porous macroreticular resins of Examples4 and 5 aresubjected to the pump test described below.

As stated previously the pump test is a severe physical stability test.In the comparison below in Table ll, a cycle consists of loading theresin for 4 minutes with 12 percent H 50 rinsing with water for 3minutes, draining for seconds, regeneration for 4 minutes with 8 percentNaOl-l, rinsing with water for 3 minutes, and draining for 30 seconds.

The bed depth is approximately 2.2 feet and the pres sure drop acrossthe bed is maintained at 33 lbs/in. /ft. The main measure of durabilityis how does the flow rate change with cycling. Tabulated are the resultsof the pump test. Included is the performance of a conventionaldivinylbenzene crosslinked macroreticular strong base ion exchangeresin.

Table ll Number of Cycles Sample: 0 I0 25 50 100 Conventional resin 9587 64 20 Example 5 99 9O 85 85* Example 6 99 95 101* *flow rate (Literper hour) EXAMPLE 7 Agel type styrene polymer crosslinked with 2 percenttrimethylolpropane trimethylacrylate is chloromethylated in aconventional manner using aluminum chloride and chloromethylmethylether. The chloromethylated intermediate so prepared from 208 parts ofcopolymer is stirred with 195.8 parts of dimethylaminoethanol at 25-30C.for 4 hours. Excess amine is removed by distillation with the additionof water to maintain a constant volume until a flask temperature of C.is reached.

The resin is cooled, backwashed to remove fines, dewatered on a Bucknerfunnel and bottled moist. The gel, anion exchange resin so obtainedcontains 51.9 percent solids and has a total anion exchange capacity of3.93 meq./g. of dry material.

EXAMPLE 8 A copolymer prepared as in Example 4 which analyses about 88percent styrene and 12 percent trimethylolpropane trimethacrylate andhaving a porosity of about 0.42 cc/cc of beads is chloromethylated in aconventional manner using chloromethyl methyl ether and aluminumchloride. The chloromethylated intermediate so prepared from 203 partsof copolymer is stirred with 195.8 parts of dimethylaminoethanol at25-30C. for 4 hours. Excess amine is removed by distillation with theaddition of water to maintain a constant volume until a flasktemperature of l00C. is reached.

The resin is cooled, backwashed to remove fines, dewatered on a Buchnerfunnel and bottled moist. The porous, macroreticular, product soobtained contains 44.2 percent solids and has a total anion exchangecapacity of 3.70 meq./g. of dry material.

Other crosslinking monomers, for example, divinylbenzene, ethyleneglycol divinyl ether, etc., may be substituted in minor amounts for thepolyfunctional methacrylate, i.e., to provide a mixture of crosslinkerswithout detracting significantly from the useful properties of the novelresins of this invention. in some cases,

the mixture of crosslinkers even improves the properties orcharacteristics of the novel resins. Thus, in the case of a mixture ofcrosslinkers containing divinylbenzene, the divinylbenzene provides fora more complete crosslinking and virtually eliminates any extractablespossibly present in the resin such as small amounts of uncrosslinkedpolystyrene which might be extracted out, for example, during aprocessing step such as the chloromethylation step. Instead of using theclassic chloromethylation procedure to prepare strong base resins, onecould alternatively use an acrylaminomethylation procedure involving thereaction of the backbone polymer with an acylomaiomethylating agent, inthe presence of a swelling or solvating agent such as, for example,ethylene dichloride or a nitropropane, followed by hydrolysis to splitoff the acyl groups and followed by alkylation to convert the resins tostrong base resins, as more fully disclosed in copending applicationSer. No. 194,496 of R Wuchter, filed Nov. 1, 1971, and

EXAMPLE 9 A series of gel resins crosslinked with mixtures of DVB(divinylbenzene) and TMPTMA (trimethylolpropane trimethylacrylate) areprepared following the procedure of Example 1, above, substitutingmixtures of DVB and TMPTMA for the TMPTMA of Example 1. The proportionsof TMPTMA and DVB are shown in Table 111 below. The balance of thecomposition in the resin beads is styrene. Also given are resultsshowing the excellent wet-dry stability, uranium adsorption capacity asU 0 in g/l and anion exchange capacity (AEC). As a measure of physicalstability, the resin beads are subjected to a wet-dry test in which thebeads are first dried at 105C. to constant weight, then cooled and thenre-wet with tap water at room temperature. The physical appearance isnoted both before and after the test and reported as percent untouched(or uncraclced) beads.

TABLE III PROPERTIES OF STRONG BASE RESlNS PREPARED FROM MIXTURES OF DVBAND TMPTMA U 0 Appearance Run TMPTMA DVB AEC Solids g/l As Is Afterperfect untouched beads 'W/D wet-dry test assigned to a common assignee,which application is EXAMPLE 1O herein incorporated by reference. Theuse of DVB as hereinabove described, prevents extractables which mightbe extracted during the acylaminomethylation procedure. The strong baseresin may also be prepared by a sulfuryl chloride technique, involvingthe use of a backbone polymer having a pendant methyl group, and asolvent and sulluryl chloride as more fully disclosed in applicationSer. No. 248,150 of .1. H. Barrett, filed A series of macroreticularresins crosslinked with mixtures DVB and TMPTMA are prepared followingthe procedure of Example 4, above, substituting mixtures of DVB andTMPTMA for the '1"MPTMA.'1he results showing the excellent pump teststability o1- these resins are given in Table IV.

MlBC methylisobutyl carbinol 'AEC anion exchange capacity Apr. 27, 1972and assigned to a common assignee,

which application is also incorporated herein by refer- 6 ence. Again,the use of the DVB in combination with the trimethylolpropanetrimethylacrylate prevents extractables which might otherwise beextracted during a processing step. Although the replacement ofa portionof the trimethylolpropane trimethylacrylate with divinylbenzene isoptional (i.e., the DVB may comprise zero percent), when using a mixtureof crosslinkers, the weight ratio of trimethylolpropanetrimethylacrylate to divinylbenzene is in the range of about 5:1 to 1:1and, more preferably, about 4:1 to 2:1.

The pump test is described earlier in the specification. The pump testdata reported above is obtained using 12 percent H SO. and 8 percentNaOH, following the procedure set forth in the first three' paragraphsof page 14, i.e., in Example 6, hereinabove.

EXAMPLE 1 l A series of polymers cross-linked with trimethylolpropanetrimethylacrylate or a mixture of TMPTMA and divinylbenzene are testedfor physical stability by the Chatillon Test." The macroreticularpolymers are prepared in accordance with the procedure Example 4.

A control polymer containing no trimethylolpropane trimethylacrylate andprepared according to the procedure of Example 4 and is also evaluated.

The Chatillon Test measures friability a property common to all ionexchange resins and copolymers and is defined as the average forcerequired to fracture individual beads. The test comprises measuringfriability by fragmenting single beads between parallel planes tosimulate the forces exerted on the resin in a commercial columnoperation. Although the sample polymers comprising 10 heads per samplewere tested in both dry and wet forms, the wet form is considered moreaccurate to indicate physical stability since it more closelyapproximates field conditions. As shown in the following TMPTMA areconsiderably stronger than polymers containing no TMPTMA.

table V, polymers containing of a polymerized mixture of from 60 percentto'99.9 percent by weight of styrene and from 0.1 percent to 40 percentof a methacrylate monomer selected from the class consisting oftrimethylolpropane trimethacrylate, pentaerithritol trimethacrylate,pentareithritol tetramethacrylate, and glycerol trimethacrylate or amixture of said methacrylate monomer with a minor iamount ofdivinylbenzene. 2. A polymer as claimed in claim 1 wherein the polymerhas a gelular nature. I

3. A polymer as claimed in claim 1 wherein the polymer has amacroreticular structure.

4. A polymer as claimed in claim 1 wherein the methacrylate monomer istrimethylolpropane trimethacrylate. 5. A polymer as claimed in claim 4wh e r ein the mix- It is also determined that to gomperlsate for thedecreased efficacy of TMPTMA as a crosslinker, more T- MPTMA must bepresent in the monomer mixture to obtain adequately crosslinkedpolymers. The quality of crosslinking is commonly understood to bedirectly related to the percent solids present in the final product.Sample 1 containing a total percent by weight DVB/TMPTMA of 7 percentshowed the same percent solids and accordingly possesses the same degreeof crosslinking as sample 6 containing a total of 5 percent by weight ofDVB.

We claim: 7 A porous, resinous polymer cpgsisting essentially turecontains about percent to 99.5 percent styrene by weight and 0.5 percentto 10 percent by weight of trimethylolpropane trimethacrylate.

6. A polymer as claimed in claim 4 wherein the mixture contains percentto 99 percent by weight of styrene and 1 percent to 5 percent by weightof trimethylolpropane trimethacrylate.

7. A polymer as claimed in claim 1 which is a polymerized mixture ofstyrene and a mixture of trimethylolpropane trimethacrylate withdivinylbenzene, the weight ratio of the trimethylolpropanetrimethacrylate to divinylbenzene being in the range of about 5:1 to

1. A PORUS, RESINOUS POLYMER CONSISTING ESSENTIALLY OF A POLYMERIZEDMIXTURE OF FROM 60 PERCENT TO 99.9 PERCENT BY WEIGHT OF STYRENE AND FROM0.1 PERCENT TO 40 PERCENT OF A METHACRYLATE MONOMER SELECTED FROM THECLASS CONSISTING OF TRIMETHYLOPROPANE TRIMETHACRYLATE, PENTAERITHRITOLTRIMETHACRYLATE, PENTAREITHRITOL TETRAMETHACRYLATE, AND GLYCEROLTRIMETHACRYLATE OR MIXTURE OF SAID METHACRYLATE MONOMER WITH A MINORAMOUNT OF DIVINYLBENZENE.
 1. A porous, resinous polymer consistingessentially of a polymerized mixture of from 60 percent to 99.9 percentby weight of styrene and from 0.1 percent to 40 percent of amethacrylate monomer selected from the class consisting oftrimethylolpropane trimethacrylate, pentaerithritol trimethacrylate,pentaerithritol tetramethacrylate, and glycerol trimethacrylate or amixture of said methacrylate monomer with a minor amount ofdivinylbenzene.
 2. A polymer as claimed in claim 1 wherein the polymerhas a gelular nature.
 3. A polymer as claimed in claim 1 wherein thepolymer has a macroreticular structure.
 4. A polymer as claimed in claim1 wherein the methacrylate monomer is trimethylolpropanetrimethacrylate.
 5. A polymer as claimed in claim 4 wherein the mixturecontains about 90 percent to 99.5 percent styrene by weight and 0.5percent to 10 percent by weight of trimethylolpropane trimethacrylate.6. A polymer as claimed in claim 4 wherein the mixture contains 95percent to 99 percent by weight of styrene and 1 percent to 5 percent byweight of trimethylolpropane trimethacrylate.